TheAB-algorithm and its properties

One presents a new algorithm, called the -algorithm, for solving the generalized eigenvalue problem Ax=λBx, where det (A—λB) ≠ 0, relative to A. The algorithm is iterative, it is based on the application of plane rotations and allows us to pass from the initial problem to the solving of a similar problem having simpler matrices, whose eigenvalues can be easily computed and coincide with the eigenvalues of the initial problem. Thus, if all the eigenvalues of the initial problem are distinct, then the application of the -algorithm leads to the computation of the eigenvalues of a pencil with triangular matrices. In the case of an arbitrary initial pencil A—λB, the problem reduces to solving the eigenvalue problem for a pencil of quasitriangular form. One proves the convergence of the algorithm. One establishes its properties which in many respects are similar with the properties of the known algorithms QR and QZ, the first of which solves the usual eigenvalue problem while the second one solves the generalized problem of the above-mentioned form.     

To solving problems of algebra for two-parameter matrices. III

The paper continues the series of papers devoted to surveying and developing methods for solving algebraic problems for two-parameter polynomial and rational matrices of general form. It considers linearization methods, which allow one to reduce the problem of solving an equation F(λ, μ)x = 0 with a polynomial two-parameter matrix F(λ, μ) to solving an equation of the form D(λ, μ)y = 0, where D(λ, μ) = A(μ)-λB(μ) is a pencil of polynomial matrices. Consistent pencils and their application to solving spectral problems for the matrix F(λ, μ) are discussed. The notion of reducing subspace is generalized to the case of a pencil of polynomial matrices. An algorithm for transforming a general pencil of polynomial matrices to a quasitriangular pencil is suggested. For a pencil with multiple eigenvalues, algorithms for computing the Jordan chains of vectors are developed. Bibliography: 8 titles. Translated from Zapiski Nauchnykh Seminarov POMI, Vol. 359, 2008, pp. 166–207.     

Solution of the partial eigenvalue problem for a regular matrix pencilD(λ) =A − λB

One presents the ALGOL procedures which implement the algorithm for the determination of the group of smallest (greatest) eigenvalues and their corresponding eigenvectors for a matrix pencil where A and B are real square matrices of simple structure. From the initial pencil one constructs a matrix C, whose eigenvalues are taken as the initial approximations to the eigenvalues from the group of the smallest (greatest) eigenvalues of the pencil. The refinement of the eigen-values is performed on the basis of the theory of perturbations. Then one determines the eigen-vectors and one computes the infinite norm of the residual. One gives ALGOL programs and test examples.     

Eigenvalue problem for a regular linear pencil of matrices close to singular ones

The solution is examined of the eigenvalue problem (1) for a regular linear pencil of matrices A and B of which at least one is close to being singular. Two groups of algorithms are proposed for solving (1). Both groups of algorithms work in the situation when the eigenvalues of the original pencil can be separated into groups of eigenvalues large and small in absolute value. The algorithms reveal this situation. The algorithms of the first group permit the passage from the original pencil to a pencil strictly equivalent to it, which in form is close to a quasitriangular pencil (or coincides with a quasitriangular one in case at least one of the pencil's matrices is singular). The eigenvalues of the diagonal blocks of the pencil constructed yield approximations to the eigenvalues of problem (1). If the approximations obtained are refined by the Newton method, using the normalized decomposition of auxiliary constructed matrices, then both the eigenvalues of (1) as well as all the linearly independent eigenvectors corresponding to them can be found. The algorithms of the second group permit the passage from the original pencil to a strictly equivalent pencil representable as a sum of two singular pencils whose null spaces are mutually perpendicular; next, with the aid of an iteration process based on the use of perturbation theory, these algorithms permit the finding of the eigenvalues of pencil (1), small (large) in absolute value, and the eigenvectors corresponding to them. Ill-conditioned regular pencils close to singular ones also are examined. For them an algorithm is suggested which permits the ill conditioning to be revealed and permits approximations to the stable (to perturbations in the original data) eigenvalues of the pencil to be obtained.Translated from Zapiski Nauchnykh Seminarov Leningradskogo Otdeleniya Matematicheskogo Instituta im. V. A. Steklova AN SSSR, Vol. 90, pp. 63–82, 1979.     

常系数线性方程组的一种新解法

对于常系数线性微分方程组:dx/dt=Ax(A是n阶实常数矩阵)通过特征根λ和对应的特征行向量K:K~T(A-λE)=0将微分方程组化为线性方程组:1°当有n个互异的特征根λ_1,λ_2,…,λ_n,对应的线性无关的特征行向量为K_1,K_2,…,K_n,若记K_i=(k_1,k_2,…,k_n)(i=1,2,…,n),则有方程组:(n∑i=1 k_ix_i)′=λ_j(n∑i=1 k_ix_I)(j=1,2,…,n);2°当有不同的特征根λ_1,λ_2,…,λ_m其重数分别为n_1,n_2,…,n_m,n_1+n_2+…+n_m=n,对应的线性无关的特征行向量为K_i=(k_1,K_2,…,k_n)(i=1,2,…,m),则有方程组:(n∑i=1 k_rx_r)′=λ_k(n∑i=1 k_rx_r)((A-λ_jE)x_(n_i)=0;i=1),(n∑i=1 k_rx_r)′=λ_j(n∑i=1k_rx_r)+c_(n_i)e~(λ_jt)((A-λ_kE)x_(i-1)=Ex_i,i=2,…,n_i).     

数量对合矩阵的线性组合的秩的不变性

若矩阵A、B满足A2=λ2I、B2=μ2I（λμ≠0）,称A、B都是数量对合矩阵．当非零复数a、b、u、v满足μλ＋bμ≠0、uλ＋vμ≠0时,我们证明了数量对合矩阵A、B与单位矩阵,的线性组合的秩总是相等,并且是一个与a、b、札、u选择都无关的常数．应用所得到数量对合矩阵的线性组合的秩的不变性,可推广已有文献的关于对合矩阵的相应结果．     

单位球面上仿Blaschke张量的特征值为常数的超曲面

设x:M~n→S~(n+1)是(n+1)-维单位球面上不含脐点的超曲面,在S~(n+1)的Moebius变换群下浸入x的四个基本不变量是:一个黎曼度量g称为Moebius度量;一个1-形式Φ称为Moebius形式;一个对称的(0,2)张量A称为Blaschke张量和一个对称的(0,2)张量B称为Moebius第二基本形式.对称的(0,2)张量D=A+λB也是Moebius不变量,称为浸入x的仿Blaschke张量,其中λ是常数,仿Blaschke张量的特征值称为仿Blaschke特征值.李海中和王长平(2003)研究了满足如下条件的超曲面:(i)Φ=0;(ii)存在可微函数λ和μ,使A+λg+μB=0.他们证明了λ和μ都是常数,并且给出了这类超曲面的分类,也就是D的特征值全相等的超曲面的分类.本文对满足如下条件的超曲面进行了分类:(i)Φ=0,(ii)对某一个常数λ,D具有两个互异的常数特征值.     

On the maximum number of disjoint triple systems

Journal of Geometry - Let D(λ;v) denote the maximum number of mutually disjoint S(λ;2,3,v). We prove that D(2;v)=v?2/2 for all v ≡ 0 or 4 (mod 6), v ≡ 0 and that...     

具有拟周期系数的schrodinger方程的可约化与平衡点的线性稳定性

对Schrodinger方程(A):iut-uxx+c(t)u=0u(t,0)=u(t,2π)=0,u(t,x)=∑∞n=1qn(t)n(x)进行讨论.n(x)是特征方程y″+λy=0y(0)=y(2π)=0中特征值对应的特征函数,c(t)=a+εc1(t),其中a是常数,c1(t)是以ω为频率的拟周期函数.直接判断方程的稳定性十分困难,把方程中的c(t)约化为常数,然后利用约化后的结果来判断方程(A)的平衡点的线性稳定性,方法简单实用.     

稳定的不变子空间的扰动界限

§1.引言 1.1.稳定的不变子空间 在矩阵的各类不变子空间中,从扰动分析的角度研究得比较深入的,是由根子空间的直和构成的不变子空间。     

参数边界条件下奇型Sturm-Liouville算子的半逆问题

Sturm-Liouville算子的半逆问题讨论由一组谱和半区间上势函数唯一确定整个区间上势函数q(x).本文利用Koyunbakan和Panakhov的方法和[13]的结论,讨论(0,π)上的奇型Sturm-Liouville问题满足-y″+[q(x)-1/4sin2x]y=λy,参数边界条件y(0,λ)=0或y′(0,λ)-hy(0,λ)=0和y′(π,λ)+(aλ+b)y(π,λ)=0,证明一组谱和(π/2,π)上的势函数q(x)唯一确定(0,π)上的势函数q(x).     

λ-重K_(1,4)-设计到λ-重K_(1,3)-最大填充的变形

令(X,B)为一个u阶的λ-重K_(1,4)-设计.对于每一个区组B=(a:b,c,d,e)∈B,若删去边{a,e},则得到一个K_(1,3)[a:b,c,d].令C为删去B中每一个区组的边{a,e}而得到的K_(1,4)的集合,F为被删去的边构成的集合.若F可以被重组成[λv(v-1)/24]个K_(1,3)的集合D,则(X,CUD)为一个v阶λ-重K_(1,3)-最大填充.称(X,C∪D)为λ-重K_(1,4-)设计(X,B)的变形.本文证明了v阶λ-重K_(1,4)-设计到u阶λ-重K_(1,3)-最大填充的变形存在的充要条件是λv(v-1)≡0(mod 8)且v≥5.     

Construction of a canonic basis for matrices and pencils of matrices

An algorithm is offered, which with insignificant modifications permits; 1) the finding of a canonic basis of the root sub space corresponding to a prescribed eigenvalue of a matrix; 2) the finding of chains of associated vectors to the eigenvectors corresponding to a prescribed eigenvalue of a regular linear pencil; 3) the finding of chains of generalized associated vectors corresponding to a prescribed eigenvalue of a regular kernel of a singular linear pencil of complete column rank of two matrices; 4) the finding of linearly independent polynomial solutions of a singular linear pencil. The algorithm consists in the construction of a finite sequence of certain auxiliary matrices the choice of which depends on the problem being solved and in the construction of a sequence of their null-spaces, enabling the obtaining of all necessary information on the unknown vectors of the canonic basis of the problem being solved.Translated from Zapiski Nauchnykh Seminarov Leningradskogo Otdeleniya Matematicheskogo Instituta im. V. A. Steklova AN SSSR, Vol. 90, pp. 46–62, 1979.     

一类具有转向点问题的n阶近似解

用Langer变换和Olver变换求得一类具有转向点问题的n阶近似解:y(x)=v(x)ψ(x),其中ψ=λ12-14×(x2-1)14,2332=-λx∫11-τ2dτ,v(z)=A(z,λ)ξ(λ23z)+B(z,λ)'ζ(λ23z).并探讨了其特征值问题,得到λn=4n+1112,n=0,1,2….由此给出了该类问题的解的一般性结论.     

A property of the character table for a finite group

A character table X of a finite group is broken up into four squares: A, B, C, and D. We establish relations via which ranks of the matrices inX are connected. In particular, ifX is an l × l-matrix, A is an s × t-matrix, and, moreover, the squares A and C are opposite, thenr(A)=r(C) + s + t − l; here.r(M) is the rank of a matrix M. Associated with such each block ofX is some integral nonnegative parameter m, and we have m=0 iff A, B, C, and D are active fragments ofX. Supported by RFFR grant No. 96-01-00488. Translated fromAlgebra i Logika, Vol. 39, No. 3, pp. 273–279, May–June, 2000.     

Construction of a fundamental series of solutions of a pencil of matrices

Solution of spectral problems for a singular polynomial pencil of matrices D () of degree s1 and sizem×n is considered. Two algorithms for constructing polynomials solutions of pencils D () are considered: the first is a modification of an algorithm proposed earlier by one of the authors for determining polynomial solutions of a linear pencil; the second algorithm is based on other ideas and consists of two steps. At the first step a finite sequence of auxiliary pencils is constructed for each of which a basis of polynomial solutions of degree zero is found. At the second step the basis so constructed are rearranged into polynomial solutions of the original polynomial pencil D(). Both algorithms make it possible to find solutions of the original pencil in order of increasing degrees. For constructing a fundamental series of solutions of the pencil D() two new algorithms are proposed which work independently with either of the algorithms mentioned above for constructing polynomial solutions by rearranging them into linearly independent solutions of the pencil.Translated from Zapiski Nauchnykh Seminarov Leningradskogo Otdeleniya Matematicheskogo Instituta im. V. A. Steklova AN SSSR, Vol. 139, pp. 74–93, 1984.     

劳勃生的特殊星像函数和特殊凸像函数

<正> 设函数w在单位圆 E_z:|z|<1上是正则的.假如f(z)在 E_z上是单叶的,那末 D_f=f(E_z)是 w 平面上单叶的区域.记这种单叶函数f(z)的全体为 S_p,S_1=S.若 D_f 以原点 w=0 为星形中心,就是说若 w_0∈D_f则缐段■整个地落在区域 D_f 中,称这种函数 f(z)是 E_z 中的星像函数,其特徵是在 E_z     

A homotopy algorithm for a symmetric generalized eigenproblem

In this paper, a homotopy algorithm for finding all eigenpairs of a real symmetric matrix pencil (A, B) is presented, whereA andB are realn×n symmetric matrices andB is a positive semidefinite matrix. In the algorithm, pencil (A, B) is first reduced to a pencil , where is a symmetric tridiagonal matrix and is a positive definite and diagonal matrix. Then, the Divide and Conquer strategy with homotopy continuation approach is used to find all eigenpairs of pencil . One can easily form the eigenpair (x,) of pencil (A, B) from the eigenpair (y, ) of pencil with a few computations. Numerical comparisons of our algorithm with the QZ algorithm in the widely used EISPACK library are presented. Numerical results show that our algorithm is strongly competitive in terms of speed, accuracy and orthogonality. The performance of the parallel version of our algorithm is also presented.Research supported in part by NSF under Grant CCR-9024840.     

四元数正则矩阵束广义特征值反问题

对于任意给定的X∈Qn×m,∧=diag(λ1,…,λm)∈Rm×m,利用奇异值分解、谱分解及QR分解分别给出了满足AX=BX∧,及XHBX=Im,AX=BX∧,的正则矩阵束(A,B)的通解表达式.